Methods for improving muscle strength

ABSTRACT

The present invention relates to methods for improving muscle strength and treating muscular dystrophy.

STATEMENT OF GOVERNMENTAL RIGHTS

The invention was made with governmental support under RO1 AR056223awarded by the National Institutes of Health. The government has certainrights in the invention.

FIELD OF THE INVENTION

The invention relates to methods for improving muscle strength andtreating muscular dystrophy.

BACKGROUND OF INVENTION

Neuromuscular diseases such as muscular dystrophy (MD) and aging weakenthe musculoskeletal system and hamper locomotion. Both conditions may becharacterized by progressive skeletal muscle weakness, defects in muscleproteins, and the death of muscle cells and tissue. Physical therapy,occupational therapy, orthotic intervention, orthopedic instruments,speech therapy, aerobic exercise, low intensity anabolic steroids, andanti-inflammatory steroid supplements may be helpful, but do not reverseor generate long lasting improvements in muscle strength withoutconsequential side effects. A continuing need exists, therefore, foralternative methods to improve skeletal, diaphragmatic, and cardiacmuscle strength in aging subjects, and subjects with neuromusculardiseases such as muscular dystrophy, either as a primary therapy or asan adjunctive steroid-sparing combination therapeutic.

REFERENCE TO COLOR FIGURES

The application file contains at least one photograph executed in color.Copies of this patent application publication with color photographswill be provided by the Office upon request and payment of the necessaryfee.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically depicts improved strength in mdx mice treated withrapamycin-loaded nanoparticle. (A) Four weeks of treatment withrapamycin-loaded nanoparticles delivered intravenously significantlyincreased weight-normalized grip strength in 14-week old mdx animals vs.groups given plain nanoparticles IV, equivalent oral doses of rapamycin,or oral placebo (p<0.012, p<0.027, and p<0.016, respectively, usingFisher's protected least significant difference at 5% significancelevel). (B) No significant difference in strength was observed forage-matched wild-type mice given either plain or rapamycin-loadednanoparticles intravenously or oral rapamycin. (C) The increase inweight-normalized strength in a subset of mdx mice treated with IVrapamycin nanoparticles occurred in both young (14-18 wk) and old (34-38wk) animals (p=0.008 using a linear contrast model comparing pre- topost-treatment differences). Absolute values of the mean change instrength between time points are shown in columns with standard errorbars. (D) Wild-type mice given similar treatment and drug-holidayexhibit no significant difference between pre- and post-treatmentstrength (p=0.598).

FIG. 2 depicts micrograph images, images of Western blots, and a graphshowing that intravenously injected nanoparticles reach the muscles inmdx animals. (A) Nanoparticles (thick arrows) are found both inside mdxmouse muscle (left panel) and in the extracellular matrix of mdx mousemuscle (right panel). Nanoparticles can be distinguished from lipiddroplets by the presence of a dark ring surrounding the circle (thinarrow). (B) ¹⁹F spectroscopy was done on excised muscles to determinethe levels of PFOB in mdx muscle. Each of the muscles surveyed showednanoparticle (PFOB) uptake 24 hrs after last systemic injection. Therewas no difference in uptake between nanoparticles and rapamycin-loadednanoparticles in any of the muscles tested (two-tailed t-test). (C)Rapamycin-loaded nanoparticles (R-NP) cause a decrease in S6 levels inmdx animals when compared to nanoparticle (NP) treatment, indicatingthat the drug rapamycin reaches the muscle tissue and exerts biologicalactivity at the cellular level. However, compared to saline treatment,the nanoparticles increased S6 phosphorylation in all four muscle groupstested, indicating potentially divergent mechanisms of action of thecomponents that could synergize to augment strength, which is a highlynovel and unexpected feature of this system. Ponceau stain of blots wasdone to confirm equivalent protein loading. This same trend is not seenin the muscles from wild-type (WT) animals. (D) Immunohistochemicalstaining of mdx diaphragm shows variations in pS6 levels between musclebundles in animals treated with nanoparticles (NP) or rapamycin-loadednanoparticles (RNP).

FIG. 3 depicts images of Western blots, and graphs showing thatnanoparticles induce autophagy in the diaphragm of mdx animals. (A-D)Representative Western blots demonstrate that both nanoparticle (NP) andrapamycin-loaded nanoparticles (RNP) increase the levels of LC3B-II inthe mdx animal, whereas saline treated animals exhibit a low level ofLC3B-II expression, even when blocked with colchicine. Wild-type, lightgrey bars. mdx, dark grey bars. (E) Both Beclin-1 and BNIP3 expressionare lower in mdx animals when compared to age-matched wild-typecontrols. (F) LC3-II levels in differentiated C2C12 cells aftertreatment with nanoparticles (NP) or rapamycin-loaded nanoparticles(RapaNP) under basal or blocked (bafilomycin-A) conditions. Both NP andRapaNP treatments cause an increase in autophagy flux.

FIG. 4 depicts two plots showing improved cardiac muscle strength inolder mdx mice treated with rapamycin-loaded nanoparticles. (A) Plotshowing ejection fraction in 18 month old WT mice treated withrapamycin-loaded nanoparticles and in untreated 18 month old WT mice.(B) Plot showing ejection fraction in 18 month old mdx mice treated withrapamycin-loaded nanoparticles and in untreated 18 month old mdx mice.

FIG. 5 depicts two plots showing improved pulling strength in olderwildtype mice treated with rapamycin-loaded nanoparticles. (A) Plotshowing pulling strength per body weight in 17 month old mdx and WT micebefore treatment with rapamycin-loaded nanoparticles. (B) Plot showingpulling strength per body weight in 18 month old mdx and wt WT miceafter treatment with rapamycin-loaded nanoparticles. (C) Plot showingside by side comparison of pulling strength per body weight in 17 monthold WT mice before treatment with rapamycin-loaded nanoparticles fromplot in (A) and pulling strength per body weight in 18 month old WT miceafter on month treatment with rapamycin-loaded nanoparticles from plotin (B). (D) Plot showing change in pulling strength per body weight inmdx and WT mice after one month treatment with rapamycin-loadednanoparticles.

FIG. 6 depicts micrograph images of diaphragm muscle in mdx animals. (A)Diaphragm muscle stained with hematoxylin and eosin. (B)Rhodamine-labeled nanoparticles in the diaphragm muscle. (C) Cy7-labeledrapamycin in the diaphragm muscle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A method for increasing muscle strength in a subject has been developed.According to the invention, it has been discovered that administrationof rapamycin-loaded nanoparticles (RNP) significantly increases musclestrength in a model of muscular dystrophy (MD) and in aging subjects.Notably, these effects are not seen with oral rapamycin alone in dosingconcentrations and amounts that are typical of clinical usage. Theinventors also discovered that administering RNPs may increase musclestrength by inducing autophagy in multiple muscle groups that areaffected heterogeneously by MD or aging.

(a) Subject

The inventors discovered that administration of rapamycin-loadednanoparticles (RNPs) increases muscle strength in a subject. In someembodiments, the subject may be an animal. Non-limiting examples of ananimal in which muscle strength may be increased include a rodent, ahuman, a livestock animal, a companion animal, a laboratory animal, or azoological animal. In one embodiment, the subject may be a rodent, e.g.a mouse, a rat, a guinea pig, etc. In another embodiment, the subjectmay be a livestock animal. Non-limiting examples of suitable livestockanimals may include pigs, cows, horses, goats, sheep, llamas andalpacas. In yet another embodiment, the subject may be a companionanimal. Non-limiting examples of companion animals may include pets suchas dogs, cats, rabbits, and birds. In another embodiment, the subjectmay be a zoological animal. As used herein, a “zoological animal” refersto an animal that may be found in a zoo. Such animals may includenon-human primates, large cats, wolves, and bears.

In some embodiments, the subject is a human. Typically, a human subjectmay be a healthy human subject, or may be suffering from muscleweakness. For instance, a subject of the invention may be suffering frommuscle weakness resulting from aging, a traumatic injury or surgery, ormay have a neuromuscular disorder that may produce muscle weakness.

In one embodiment, the human subject may be healthy. In anotherembodiment, the subject may be suffering from muscle weakness resultingfrom a traumatic injury or surgery. As used herein, “trauma” is a bodywound or shock produced by sudden physical injury as from violence oraccident or a physical wound or injury, such as a fracture, blow, orsurgical procedure, which results in major muscle tissue damage.

In yet another embodiment, the subject may be suffering from muscleweakness resulting from aging. An aging human subject may be at leastabout 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 years of age orolder.

In another embodiment, the subject may be suffering from heart failure.For instance, a subject may be suffering from heart failure due tocoronary artery disease; atherosclerosis; hypertrophic cardiomyopathysuch as idiopathic or non-obstructive hypertrophic cardiomyopathy;congenital, hypertensive, or infectious heart disease; heart failureinduced by toxic substances such as drugs, heavy metals, radiation; ordue to diastolic heart failure.

In still another embodiment, the human subject may have a neuromusculardisorder that may produce muscle weakness. As used herein,“neuromuscular disorder” refers to a disorder that affects theperipheral nervous system. The peripheral nervous system includesmuscles, the nerve-muscle (neuromuscular) junction, peripheral nerves inthe limbs, and the motor-nerve cells in the spinal cord. Non-limitingexamples of neuromuscular disorders may include polymyalgia rheumatica(muscle rheumatism), polymyositis, dermatomyositis, bramaticosis andinclusion body myositis, rhabdomyolysis, amyotrophic lateral sclerosis,asarcoglycanopathy, multiple sclerosis, myasthenia gravis, musculardystrophy, spinal and bulbar muscular atrophy of Kennedy, late-onsetFinkel type spinal muscular atrophy, spinal muscular atrophy-1, spinalmuscular atrophy-2, spinal muscular atrophy-3, spinal muscularatrophy-4, spinal muscular atrophy, distal, type V, spinal muscularatrophy, distal, type V, spinal muscular atrophy juvenile, and spinalmuscular atrophy with respiratory distress.

In some embodiments, the subject has muscular dystrophy. As used herein,“muscular dystrophy” refers to a disorder in which strength and musclebulk gradually decline. Non-limiting examples of muscular dystrophydiseases may include Becker muscular dystrophy, tibial musculardystrophy, Duchenne muscular dystrophy, Emery-Dreifuss musculardystrophy, facioscapulohumeral muscular dystrophy, sarcoglycanopathies,congenital muscular dystrophy such as congenital muscular dystrophy dueto partial LAMA2 deficiency, merosin-deficient congenital musculardystrophy, type 1D congenital muscular dystrophy, Fukuyama congenitalmuscular dystrophy, limb-girdle type 1A muscular dystrophy, limb-girdletype 2A muscular dystrophy, limb-girdle type 2B muscular dystrophy,limb-girdle type 2C muscular dystrophy, limb-girdle type 2D musculardystrophy, limb-girdle type 2E muscular dystrophy, limb-girdle type 2Fmuscular dystrophy, limb-girdle type 2G muscular dystrophy, limb-girdletype 2H muscular dystrophy, limb-girdle type 21 muscular dystrophy,limb-girdle type 21 muscular dystrophy, limb-girdle type 2J musculardystrophy, limb-girdle type 2K muscular dystrophy, limb-girdle type ICmuscular dystrophy, rigid spine muscular dystrophy with epidermolysisbullosa simplex, oculopharyngeal muscular dystrophy, Ullrich congenitalmuscular dystrophy, and Ullrich scleroatonic muscular dystrophy. In anexemplary embodiment, the subject has Duchenne muscular dystrophy.

Methods of diagnosing a subject with muscle weakness, musculardystrophy, heart failure, and the like are known in the art.

In some embodiments, the subject may be a lab animal. Non-limitingexamples of a lab animal may include a rabbit, a mouse, a guinea pig, ahamster, or a rat. In one embodiment, the subject may be a lab animal.In preferred embodiments, the lab animal may be a model animal for aneuromuscular disease. Non-limiting examples of lab animals that may beused as models for neuromuscular disease may include the mdx mouseDuschenne muscular dystrophy (DMD) model, the canine golden retrievermuscular dystrophy (MD) model, the SJL/J mouse autosomal recessivelimb-girdle MD model, the B1014.6 hamster sarcoglycanopathies (SG) modeland other sarcoglycan null mutant animal models, the dy/dy(dystrophia-muscularis) mouse and the dy2J/dy2J mouse models forcongenital MD, the myodystrophy mouse (Largemyd) model, and pigcomprising mutations in the porcine Ryr1 gene as a model for malignanthyperthermia and Central Core myopathy.

In some embodiments, RNP may be administered to a culture of musclecells. Non-limiting examples of cultured muscle cells may include amyoblast cell line that give rise to muscle cells, or differentiatedmuscle cells or myocytes. The muscle cells may be, or the myoblasts maygive rise to skeletal muscle, smooth muscle, or cardiac muscle. In someembodiments, RNP may be administered to ex vivo muscle cells derivedfrom a subject.

(b) Muscle Strength

In some embodiments, the method comprises administering RNPs to asubject to increase muscle strength. According to the invention, musclestrength may be increased by RNP interaction with the mTORC1 pathway.The inventors discovered that RNP interaction with the mTORC1 pathwaymay increase muscle strength by inducing autophagy and attenuatingmuscle destruction or reducing inflammation. In some embodiments, musclestrength may be increased by attenuating muscle destruction or reducinginflammation. In other embodiments, muscle strength may be increased byinducing autophagy.

In other embodiments, the method comprises administering RNPs toincrease muscle strength in a subject suffering from muscle weaknessresulting from a traumatic injury or surgery. In one embodiment,administering RNPs to a subject suffering from muscle weakness resultingfrom a traumatic injury or surgery increases muscle strength by inducingautophagy. In another embodiment, administering RNPs to a subjectsuffering from muscle weakness resulting from a traumatic injury orsurgery increases muscle strength by attenuating muscle destruction. Inyet another embodiment, administering RNPs to a subject suffering frommuscle weakness resulting from a traumatic injury or surgery increasesmuscle strength by reducing inflammation.

In yet other embodiments, the method comprises administering RNPs to asubject suffering from muscle weakness resulting from aging to increasemuscle strength. In one embodiment, administering RNPs to a subjectsuffering from muscle weakness resulting from aging increases musclestrength by inducing autophagy. In another embodiment, administeringRNPs to a subject suffering from muscle weakness resulting from agingincreases muscle strength by attenuating muscle destruction. In anotherembodiment, administering RNPs to a subject suffering from muscleweakness resulting from aging increases muscle strength by reducinginflammation.

In other embodiments, the method comprises administering RNPs to asubject with muscular dystrophy to increase muscle strength. In oneembodiment, administering RNPs to a subject with muscular dystrophyincreases muscle strength by inducing autophagy. In another embodiment,administering RNPs to a subject with muscular dystrophy increases musclestrength by attenuating muscle destruction. In yet another embodiment,administering RNPs to a subject with muscular dystrophy increases musclestrength by reducing inflammation.

In some embodiments, administering RNPs induces autophagy in musclecells. In another embodiment, administering RNPs attenuates muscledestruction. In yet another embodiment, administering RNPs reducesinflammation.

Methods of measuring muscle strength are known in the art. In general,methods of measuring muscle strength and function vary depending on themuscle groups to be measured, and the animal whose muscle strength isbeing measured. In humans for instance, abdominal muscle strength may bemeasured using a sit-up test, the chair stand may be used to measurelower body muscle strength and function, the arm curl test may be usedto measure upper body muscle strength, and leg strength may be measuredusing the maximum voluntary contraction (MVC), which measures the peakforce produced by a muscle as it contracts while pulling against animmovable object. Diaphragm strength may be measured by standardpulmonary function tests. Cardiac strength may be measured byechocardiography, invasive right and left heart cardiac catheterization,CT, MRI, PET, or other imaging tests known to clinicians. In animalmodels such as the mouse, muscle strength may be measured using forelimbgrip strength, treadmill exercise time over some interval of time,swimming time, or other like physical measure. Other suitable means ofmeasuring muscle strength are known in the art. Similarly, methods ofmeasuring autophagy are known in the art.

In some embodiments, muscle strength may be improved by about 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,27, 28, 29, or 30% or more after a subject is administered RNP comparedto before the subject is administered RNP. In other embodiments, musclestrength may be improved by about 20, 21, 22, 23, 24, 25, 26, 27, 28,29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46,47, 48, 49 or 50% or more after a subject is administered RNP comparedto before the subject is administered RNP. In yet other embodiments,muscle strength may be improved by about 10, 15, 20, 25, 30, 35, 40, 45,50, 55, 60, 65% or more after a subject is administered RNP compared tobefore the subject is administered RNP. In an exemplary alternative ofthe embodiments, muscle strength may be improved about 7-9% after asubject is administered RNP compared to before the subject isadministered RNP. In another exemplary alternative of the embodiments,muscle strength may be improved about 13-15% after a subject isadministered RNP compared to before the subject is administered RNP. Inyet another exemplary alternative of the embodiments, muscle strengthmay be improved about 25-30% after a subject is administered RNPcompared to before the subject is administered RNP.

(c) Nanoparticles

The method of the invention comprises administering rapamycin-loadednanoparticles (RNP). As used herein, “nanoparticle” is used to refer toa nanostructure that is typically between about 5 nM and 400 nM acrossthe largest dimension of the structure. A nanoparticle of the inventionmay be spherical, but is not required to be spherical. Regardless of theshape of the nanoparticle, the nanoparticle should be capable ofcomprising rapamycin.

Non-limiting examples of suitable nanoparticles may include liposomes,poloxamers, microemulsions, micelles, dendrimers and otherphospholipid-containing systems, and perfluorocarbon nanoparticles.

In one embodiment, a liposome delivery vehicle may be utilized.Liposomes, depending upon the embodiment, are suitable for delivery ofrapamycin in view of their structural and chemical properties. Generallyspeaking, liposomes are spherical vesicles with a phospholipid bilayermembrane. The lipid bilayer of a liposome may fuse with other bilayers(e.g., the cell membrane), thus delivering the contents of the liposometo cells.

Liposomes may be comprised of a variety of different types ofphosholipids having varying hydrocarbon chain lengths. Phospholipidsgenerally comprise two fatty acids linked through glycerol phosphate toone of a variety of polar groups. Suitable phospholipids includephosphatidic acid (PA), phosphatidylserine (PS), phosphatidylinositol(PI), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG),phosphatidylcholine (PC), and phosphatidylethanolamine (PE). The fattyacid chains comprising the phospholipids may range from about 6 to about26 carbon atoms in length, and the lipid chains may be saturated orunsaturated. Suitable fatty acid chains include (common name presentedin parentheses) n-dodecanoate (laurate), n-tetradecanoate (myristate),n-hexadecanoate (palmitate), n-octadecanoate (stearate), n-eicosanoate(arachidate), n-docosanoate (behenate), n-tetracosanoate (lignocerate),cis-9-hexadecenoate (palmitoleate), cis-9-octadecanoate (oleate),cis,cis-9,12-octadecandienoate (linoleate), all cis-9, 12,15-octadecatrienoate (linolenate), and allcis-5,8,11,14-eicosatetraenoate (arachidonate). The two fatty acidchains of a phospholipid may be identical or different. Acceptablephospholipids include dioleoyl PS, dioleoyl PC, distearoyl PS,distearoyl PC, dimyristoyl PS, dimyristoyl PC, dipalmitoyl PG,stearoyl,oleoyl PS, palmitoyl,linolenyl PS, and the like.

The phospholipids may come from any natural source, and, as such, maycomprise a mixture of phospholipids. For example, egg yolk is rich inPC, PG, and PE, soy beans contains PC, PE, PI, and PA, and animal brainor spinal cord is enriched in PS. Phospholipids may come from syntheticsources too. Mixtures of phospholipids having a varied ratio ofindividual phospholipids may be used. Mixtures of differentphospholipids may result in liposome compositions having advantageousactivity or stability of activity properties. The above mentionedphospholipids may be mixed, in optimal ratios with cationic lipids, suchas N-(1-(2,3-dioleolyoxy)propyl)-N,N,N-trimethyl ammonium chloride,1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine,3,3′-deheptyloxacarbocyanine iodide,1,1′-dedodecyl-3,3,3′,3′-tetramethylindocarbocyanine perchloarate,1,1′-dioleyl-3,3,3′,3′-tetramethylindo carbocyanine methanesulfonate,N-4-(delinoleylaminostyryl)-N-methylpyridinium iodide, or1,1,-dilinoleyl-3,3,3′,3′-tetramethylindocarbocyanine perchloarate.

Liposomes may optionally comprise sphingolipids, in which sphingosine isthe structural counterpart of glycerol and one of the fatty acids of aphosphoglyceride, or cholesterol, a major component of animal cellmembranes. Liposomes may optionally contain pegylated lipids, which arelipids covalently linked to polymers of polyethylene glycol (PEG). PEGsmay range in size from about 500 to about 10,000 daltons.

Liposomes may further comprise a suitable solvent. The solvent may be anorganic solvent or an inorganic solvent. Suitable solvents include, butare not limited to, dimethylsulfoxide (DMSO), methylpyrrolidone,N-methylpyrrolidone, acetronitrile, alcohols, dimethylformamide,tetrahydrofuran, or combinations thereof.

Liposomes carrying the composition of the invention may be prepared byany known method of preparing liposomes for drug delivery, such as, forexample, detailed in U.S. Pat. Nos. 4,241,046, 4,394,448, 4,529,561,4,755,388, 4,828,837, 4,925,661, 4,954,345, 4,957,735, 5,043,164,5,064,655, 5,077,211 and 5,264,618, the disclosures of which are herebyincorporated by reference in their entirety. For example, liposomes maybe prepared by sonicating lipids in an aqueous solution, solventinjection, lipid hydration, reverse evaporation, or freeze drying byrepeated freezing and thawing. In a preferred embodiment the liposomesare formed by sonication. The liposomes may be multilamellar, which havemany layers like an onion, or unilamellar. The liposomes may be large orsmall. Continued high-shear sonication tends to form smaller unilamellarlipsomes.

As would be apparent to one of ordinary skill, all of the parametersthat govern liposome formation may be varied. These parameters include,but are not limited to, temperature, pH, concentration of methioninecompound, concentration and composition of lipid, concentration ofmultivalent cations, rate of mixing, presence of and concentration ofsolvent.

In another embodiment, the composition of the invention may be deliveredto a tissue or cell as a microemulsion. Microemulsions are generallyclear, thermodynamically stable solutions comprising an aqueoussolution, a surfactant, and “oil.” The “oil” in this case, is thesupercritical fluid phase. The surfactant rests at the oil-waterinterface. Any of a variety of surfactants are suitable for use inmicroemulsion formulations including those described herein or otherwiseknown in the art. The aqueous microdomains suitable for use in theinvention generally will have characteristic structural dimensions fromabout 5 nm to about 100 nm. Aggregates of this size are poor scatterersof visible light and hence, these solutions are optically clear, butalso may appear as a milky colloidal suspension depending on exactcomposition, storage conditions, pH, temperature, surface charge, shape,and such. As will be appreciated by a skilled artisan, microemulsionscan and will have a multitude of different microscopic structuresincluding sphere, rod, or disc shaped aggregates. In one embodiment, thestructure may be micelles, which are the simplest microemulsionstructures that are generally spherical or cylindrical objects. Micellesare like drops of oil in water, and reverse micelles are like drops ofwater in oil. In an alternative embodiment, the microemulsion structureis the lamellae. It comprises consecutive layers of water and oilseparated by layers of surfactant. The “oil” of microemulsions mayoptimally comprise phospholipids, although other hydrophobic corecomponents singularly or in mixtures (e.g., perfluorocarbons: see below)may contribute to the composition of the particle. Any of thephospholipids detailed above for liposomes are suitable for embodimentsdirected to microemulsions. The composition of the invention may beencapsulated in a microemulsion by any method generally known in theart.

In yet another embodiment, the composition of the invention may bedelivered in a dendritic macromolecule, or a dendrimer. Generallyspeaking, a dendrimer is a branched tree-like molecule, in which eachbranch is an interlinked chain of molecules that divides into two newbranches (molecules) after a certain length. This branching continuesuntil the branches (molecules) become so densely packed that the canopyforms a globe. Generally, the properties of dendrimers are determined bythe functional groups at their surface. For example, hydrophilic endgroups, such as carboxyl groups, would typically make a water-solubledendrimer. Alternatively, phospholipids may be incorporated in thesurface of a dendrimer to facilitate absorption across the skin. Any ofthe phospholipids detailed for use in liposome embodiments are suitablefor use in dendrimer embodiments. Any method generally known in the artmay be utilized to make dendrimers and to encapsulate or conjugaterapamycin via standard linker chemistries known in the art. For example,dendrimers may be produced by an iterative sequence of reaction steps,in which each additional iteration leads to a higher order dendrimer.Consequently, they have a regular, highly branched 3D structure, withnearly uniform size and shape. Furthermore, the final size of adendrimer is typically controlled by the number of iterative steps usedduring synthesis. A variety of dendrimer sizes are suitable for use inthe invention. Generally, the size of dendrimers may range from about 1nm to about 100 nm.

In preferred embodiments, a nanoparticle of the invention may be aperfluorocarbon nanoparticle. Such nanoparticles are known in the art.For instance, see U.S. Pat. Nos. 5,690,907; 5,780,010; 5,989,520 and5,958,371, each hereby incorporated by reference in their entirety.

Useful perfluorocarbon emulsions are disclosed in U.S. Pat. Nos.4,927,623, 5,077,036, 5,114,703, 5,171,755, 5,304,325, 5,350,571,5,393,524, and 5,403,575 and include those in which the perfluorocarboncompound is perfluorodecalin, perfluorooctane, perfluorodichlorooctane,perfluoro-n-octyl bromide, perfluoroheptane, perfluorodecane,perfluorocyclohexane, perfluoromorpholine, perfluorotripropylamine,perfluortributylamine, perfluorodimethylcyclohexane,perfluorotrimethylcyclohexane, perfluorodicyclohexyl ether,perfluoro-n-butyltetrahydrofuran, and compounds that are structurallysimilar to these compounds and are partially or fully halogenated(including at least some fluorine substituents) or partially or fullyperfluorinated including perfluoroalkylated ether, polyether or crownether. In some embodiments, the perfluorocarbon compound isperfluoro-n-octyl bromide. In other embodiments, the perfluorocarboncompound may be a perfluoroalkylated crown ether.

The coating which comprises lipid/surfactant to form an outer coating onthe nanoparticles may include natural or synthetic phospholipids, fattyacids, cholesterols, lysolipids, sphingomyelins, and the like, includinglipid conjugated polyethylene glycol. Various commercial anionic,cationic, and nonionic surfactants can also be employed, includingTweens, Spans, Tritons, and the like. Some surfactants are themselvesfluorinated, such as perfluorinated alkanoic acids such asperfluorohexanoic and perfluorooctanoic acids, perfluorinated alkylsulfonamide, alkylene quaternary ammonium salts and the like. Inaddition, perfluorinated alcohol phosphate esters can be employed.Cationic lipids, including DOTMA,N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride; DOTAP,1,2-dioleoyloxy-3-(trimethylammonio)propane; DOTB,1,2-dioleoyl-3-(4′-trimethyl-ammonio)butanoyl-sn-glycerol,1,2-diacyl-3-trimethylammonium-propane;1,2-diacyl-3-dimethylammonium-propane; 1,2-diacyl-sn-glycerol-3-ethylphosphocholine; and3.beta.-[N′,N′-dimethylaminoethane)-carbamol]cholesterol-HCl, may alsobe used.

Perfluorocarbon nanoparticles are typically formed by microfluidizing amixture of the fluorocarbon lipid which forms the core and thelipid/surfactant mixture which forms the outer layer in suspension inaqueous medium to form an emulsion. Sonication or other techniques maybe required to obtain a suspension of the lipid/surfactant in theaqueous medium. The components of the outer layer may also be coupled toimaging agents or radionuclides.

In some embodiments, the RNPs may be targeted to muscle tissue. Methodsof targeting nanoparticles are known in the art. For instance, targetednanoparticles may comprise targeting molecules. Alternatively, theprominent inflammatory response and consequential increased vascularpermeability, together with enhanced sarcolemmal membrane permeabilityobserved in muscle tissue of subjects with neuromuscular disease mightestablish favorable conditions for effective targeting of thenanoparticle, in analogy to the mechanism of enhanced permeability andretention (EPR) utilized in cancer nanotherapeutics.

In some embodiments, the RNPs are targeted to muscle tissue using EPR.In other embodiments, the nanoparticle may further comprise targetingmolecules, such that nanoparticles comprising targeting molecules may bedelivered and concentrated at desired sites. Targeted nanoparticles mayinclude a wide variety of targeting molecules, including but not limitedto, antibodies, antibody fragments, peptides, small molecules,polysaccharides, nucleic acids, aptamers, peptidomimetics, othermimetics and drugs alone or in combination. These targeting moleculesmay be utilized to specifically bind the nanoparticles to cellularepitopes and receptors, and may be attached directly or indirectly tothe nanoparticle.

Direct attachment of the targeting molecules to the nanoparticle refersto the preparation of a targeting molecule-nanoparticle complex whereinthe targeting molecule is covalently bound to the nanoparticle.Alternatively, direct attachment also may refer to the preparation of atargeting molecule-nanoparticle complex wherein the targeting moleculeis covalently bound to a linker, which is in turn bound to thenanoparticle.

Indirect attachment refers to forming a complex between the nanoparticleand the targeting molecule in vivo in two or more steps. Indirectattachment utilizes a chemical linking system to produce the close andspecific apposition of the nanoparticle to a targeted cell or tissuesurface. A non-limiting example of an indirect targeting system isavidin-biotin.

Avidin-biotin interactions are useful noncovalent targeting systems thathave been incorporated into many biological and analytical systems andselected in vivo applications. Avidin has a high affinity for biotin(10-15 M) facilitating rapid and stable binding under physiologicalconditions. Targeted systems utilizing this approach are administered intwo or three steps, depending on the formulation. Typically, abiotinylated ligand, such as a monoclonal antibody, is administeredfirst and “pretargeted” to the unique molecular epitopes. Next, avidinis administered, which binds to the biotin moiety of the “pretargeted”ligand. Finally, the biotinylated nanoparticle is added and binds to theunoccupied biotin-binding sites remaining on the avidin therebycompleting the biotinylated ligand-avidin-nanoparticle “sandwich”. Theavidin-biotin approach can avoid accelerated, premature clearance oftargeted particles by the mononuclear phagocyte system (MPS) secondaryto the presence of surface antibody. Additionally, avidin, with fourindependent biotin-binding sites provides signal amplification andimproves detection sensitivity.

A targeting molecule may be directly attached to a nanoparticle by avariety of methods depending upon the nature of the targeting moleculeand the nanoparticle. Direct chemical conjugation of targeting moleculesto proteinaceous nanoparticles often take advantage of numerousamino-groups (e.g. lysine) inherently present within the nanoparticle.Alternatively, functionally active chemical groups such as maleimide orNHS groups may be incorporated into the nanoparticle as chemical “hooks”for targeting molecule conjugation after the nanoparticles are formed.Another common approach is to activate polymer carboxylates withcarbodiimide prior to targeting molecule addition. Alternatively, cellmembrane inserting peptide linkers may be used to attach the drug cargoto the nanoparticle in a postformulation step as described previously inU.S. patent application Ser. No. 12/910,385, the disclosure of which ishereby incorporated by reference in its entirety.

The selected covalent attachment strategy is primarily determined by thechemical nature of the targeting molecule. For instance, monoclonalantibodies and other large proteins may denature under harsh processingconditions whereas the bioactivity of carbohydrates, short peptides,aptamers, drugs or peptidomimetics often can be preserved under theseconditions.

To ensure high targeting molecule binding integrity and maximizetargeted particle avidity flexible linkers, e.g. polyethylene glycol,amino acids or simple caproate bridges, can be inserted between thenanoparticle and the targeting molecule. These linkers may be 2 nm orlonger and may minimize interference of targeting molecule binding bynanoparticle surface interactions. Non-limiting examples of linkers mayinclude carbodiimide linkers and N-hydroxysuccinimide esters. Thelinkers may be heterobifunctional or homobifunctional.

In some embodiments, the rapamycin or rapamycin analogue may bedelivered to the muscle in a depot. As used herein, “depot” refers toany delivery mechanism known in the art to concentrate and release therapamycin or a rapamycin analogue in the muscle tissue over time toprovide a pharmaceutically effective amount. For instance, in someembodiments, injectable depot forms are made by forming microencapsulematrices of inhibitor(s) in biodegradable polymers such aspolylactide-polyglycolide. Depending on the ratio of drug to polymer,and the nature of the particular polymer employed, the rate of drugrelease can be controlled. Examples of other biodegradable polymersinclude poly(orthoesters) and poly(anhydrides). Depot injectableformulations are also prepared by entrapping the drug in liposomes ormicroemulsions which are compatible with body tissue. (see, forinstance, Chamberlain et al. Arch. Neuro. 50: 261-264, 1993; Katri etal. J. Pharm. Sci. 87: 1341-1346, 1998; Ye et al., J. Control Release64: 155-166, 2000; and Howell, Cancer J. 7: 219-227, 2001). In certainembodiments, a nanoparticle as described above serves as the depot.

(d) Rapamycin-Loaded Nanoparticles

The method of the invention utilizes rapamycin-loaded nanoparticles.Rapamycin binds the cytosolic protein FK-binding protein 12 (FKBP12) andinhibits the mammalian target of rapamycin (mTOR) pathway by directlybinding the mTOR Complex1 (mTORC1). As such, nanoparticles of theinvention may be loaded with any compound capable of inhibiting the mTORpathway. In some embodiments, the nanoparticles may be loaded withrapamycin or a rapamycin analog. Non-limiting examples of rapamycinanalogs that may be used in the invention may include CCI-779(Temsirolimus), C20-methallylrapamycin, C16-(S)-3-methylindolerapamycin,C16-iRap, AP21967 (C16-AiRap), and AP23573. In some embodiments, thenanoparticles may be loaded with CCI-779. In other embodiments, thenanoparticles may be loaded with C20-methallylrapamycin. In yet otherembodiments, the nanoparticles may be loaded withC16-(S)-3-methylindolerapamycin. In still other embodiments, thenanoparticles may be loaded with C16-iRap. In further embodiments, thenanoparticles may be loaded with AP21967. In yet still otherembodiments, the nanoparticles may be loaded with AP23573. In preferredembodiments, the nanoparticles may be loaded with rapamycin. In anotherpreferred embodiment, the nanoparticles may be loaded with one or moreinducers of autophagy. Non-limiting examples may include inhibitors ofmTOR, such as tamoxifen, perhexiline, amiodaronel, niclosamide,rottlerin, torin1, PI103 and structurally related compounds, phenethylisothiocyanate (PEITC), and dexamethasone, or mTOR independent inducers,such as lithium, carbamazepine, sodium valproate, verapamil, loperamide,amiodaronel, nimodipine, nitrendipine, niguldipine, nicardipine,pimozide, calpastatin, calpeptin, clonidine, rilmenidine,2′,5′-Dideoxyadenosine, NF449, minoxidil, penitrem A, trehalose,spermidine, resveratrol, fluspirilene, trifluoperazine, SMERs (SMER10,SMER18, SMER28 and analogs), and dorsomorphin. Other potentiallysuitable autophagy inducers may be known in the art.

Methods of incorporating compositions such as rapamycin into deliveryvehicles are known in the art and described above. In exemplaryembodiments, rapamycin may be incorporated into PFC nanoparticles asdescribed in the Examples. In other embodiments, conjugation ofrapamycin to lipid, peptide or other linkers that insert into thenanoparticle membrane may be used. In other embodiments, rapamycyincarried in the core of the particle (e.g., liposomes) may be used. Theconcentration of rapamycin in the nanoparticles can and will vary. Insome embodiments, the RNP particles may comprise about 0.1, 0.2, 0.3,0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or about 1 mole % rapamycin or rapamycinanalogue. In other embodiments, the RNP particles may comprise about0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, or about 0.3mole % rapamycin or rapamycin analogue. In yet other embodiments, theRNP particles may comprise about 0.271, 0.272, 0.273, or 0.274, 0.275,0.276, 0.277, 0.278, 0.279, 0.28, 0.281, 0.282, 0.283, 0.284, or 0.285mole % rapamycin or rapamycin analogue. In an exemplary embodiment, theRNP particles comprise about 0.275 mole % rapamycin or rapamycinanalogue.

(e) Administration

Nanoparticles comprising rapamycin may be administered to a subject byseveral different means. For instance, nanoparticles may generally beadministered parenteraly, intraperitoneally, intravascularly, orintrapulmonarily in dosage unit formulations containing conventionalnontoxic pharmaceutically acceptable carriers, adjuvants, and vehiclesas desired. The term parenteral as used herein includes subcutaneous,intravenous, intramuscular, intrathecal, or intrasternal injection, orinfusion techniques. In one embodiment, the composition may beadministered in a bolus. In a preferred embodiment, the composition maybe administered intravenously. Formulation of pharmaceuticalcompositions is discussed in, for example, Hoover, John E., Remington'sPharmaceutical Sciences, Mack Publishing Co., Easton, Pa. (1975), andLiberman, H. A. and Lachman, L., Eds., Pharmaceutical Dosage Forms,Marcel Decker, New York, N.Y. (1980).

Injectable preparations, for example, sterile injectable aqueous oroleaginous suspensions, may be formulated according to the known artusing suitable dispersing or wetting agents and suspending agents. Thesterile injectable preparation may also be a sterile injectable solutionor suspension in a nontoxic parenterally acceptable diluent or solvent.Among the acceptable vehicles and solvents that may be employed arewater, Ringer's solution, and isotonic sodium chloride solution. Inaddition, sterile, fixed oils are conventionally employed as a solventor suspending medium. For this purpose, any bland fixed oil may beemployed, including synthetic mono- or diglycerides. In addition, fattyacids such as oleic acid are useful in the preparation of injectables.Dimethyl acetamide, surfactants including ionic and non-ionicdetergents, and polyethylene glycols can be used. Mixtures of solventsand wetting agents such as those discussed above are also useful.

The RNPs may be administered to a subject once, or multiple times. Insome preferred embodiments, the RNPs may be administered once. In otherpreferred embodiments, the RNPs may be administered multiple times. Whenadministered multiple times, the RNPs may be administered at regularintervals or at intervals that may vary during the treatment of asubject. In some embodiments, the RNPs may be administered multipletimes at intervals that may vary during the treatment of a subject. Inpreferred embodiments, the RNPs may be administered multiple times atregular intervals. In some alternatives of the preferred embodiments,the RNPs may be administered at intervals of about 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, or more days. In other alternatives of thepreferred embodiments, the RNPs may be administered at intervals ofabout 1, 2, 3, 4, 5, 6, 7, 8 or more weeks. In yet other alternatives ofthe preferred embodiments, the RNPs may be administered at intervals ofabout 1, 2, 3 or more months. In preferred embodiments, the RNPs may beadministered twice weekly.

One of skill in the art will recognize that the amount and concentrationof the composition administered to a subject will depend in part on thesubject and the reason for the administration (i.e. imaging, drugdelivery, etc.). Methods for determining optimal amounts are known inthe art. In some embodiments, the RNPs may be administered to thesubject in an amount of about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2 mL per kilogramof the subject. In other embodiments, the RNPs may be administered tothe subject in an amount of about 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 mLor more per kilogram of the subject.

EXAMPLES

The following examples are included to demonstrate preferred embodimentsof the invention.

Introduction for Examples 1-4

Duchenne muscular dystrophy (DMD) is an X-linked progressive muscledegenerative disorder that affects 1:3500 males and is caused bymutations in the dystrophin gene leading to complete absence ofdystrophin protein [1]. In contractile tissues, dystrophin is known toplay a role in anchoring the cytoskeleton of a muscle cell to the basallamina. Without proper attachments, coordinated contraction cannot beachieved, explaining in part the weakness observed in these boys.Progressive deterioration of function results from repeated cellularinjury as sarcolemmal membranes are susceptible to tearing anddisruption as patients age. Primary defects in calcium kinetics havebeen ascribed to alterations in calcium channel regulatory proteins thatcontribute to progressive muscle fatigue and failure. Indeed, musclebiopsy specimens from DMD patients have demonstrated an increase incalcium within the muscle cells that can induce apoptosis [2, 3].

Additionally, a strong inflammatory response occurs in the musclecompartment that reflects the age of the process [2]. This immuneresponse is postulated to be a response to cellular necrosis that isamplified based on the large number of cells that are constantly beingdestroyed and regenerated. The amplified immune infiltration has becomethe target of therapy with some success. Currently, the only validatedtherapies for these patients are corticosteroids, which improve strengthand overall survival by a combination of membrane stabilization andanti-inflammatory actions [4-7]. Alternative experimental therapiesinclude genetic manipulation to partially restore dystrophin [8], betablockers [9], and antifibrotic agents [10].

Although a number of animal models of muscular dystrophy exist, the mdxmouse is used extensively for validating proposed therapeuticinterventions. The progression of disease and muscle pathology issimilar in this animal to human disease, despite being somewhat mild inphenotype [11]. The mdx mouse exhibits three phases of disease, eachhallmarked by different microscopic findings. From the time of weaningto 10 weeks of age, the strength in mdx mice improves as they arerapidly growing. From three weeks to 7 weeks, there is an increase inmuscle necrosis, thus rendering this period non-ideal for druginterventions that rely on strength measurement outcomes. From 10 weeksto 24 weeks, a period of rapid decline in body weight-normalizedstrength ensues as the muscles simultaneously become weaker and themouse gains weight. The mouse maintains a basal level of muscledegeneration and regeneration throughout this period [12]. Beyond 24weeks, mice experience a progressive decline in strength [13].

Recent provocative reports of the use of rapamycin to restore musclephenotype in dystrophic mice have emerged providing another testableapproach to ameliorate the inexorable disease process [14, 15].Rapamycin is an immune-suppressing macrolide used to prevent organtransplant rejection and as an anti-inflammatory agent to preventangioplasty restenosis [16-18]. By binding to the mammalian target ofrapamycin complex 1 (mTORC1), rapamycin blocks pro-proliferative,anti-apoptotic signaling [19]. mTORC1 serves as a central node inmetabolically active cells with high turnover rates and phosphorylatesp70 S6K and 4E-BP1 to promote protein translation by increasingribosomal synthesis and cap-dependent translation machinery, leading tocell growth. Paradoxically, blocking mTORC1 with rapamycin might beexpected to exert deleterious effect on protein synthesis, muscle fiberregeneration, and cell growth in mdx mice. However, rapamycin has alsobeen shown to induce autophagy, a cell survival mechanism that enablesthe cell to recycle amino acids via the non-specific degradation oflong-lived proteins and dysfunctional organelles [20] and may representa novel mechanism for its unexpected action.

Materials and Methods for Examples 1-4

All chemicals were purchased from Sigma-Aldrich, Inc. (St. Louis, Mo.)unless otherwise specified.

Nanoparticle Formulation

The nanoparticle emulsions were prepared in the following manner. Asurfactant co-mixture (600 mg) was prepared by combining 98 mole %purified egg phosphatidylcholine (Avanti Polar Lipids, #840051P) and 2mole % DPPE (Avanti Polar Lipids, #850705P) and (for the drug containingemulsion only) 0.275 mole % of rapamycin, dissolving the mixture in 3:1chloroform/methanol, and removing the solvent in vacuo at 40° C. To thedried lipid mixture, 23.4 ml of deionized water containing 2.5% (v/v) ofglycerol was added and the lipid reconstituted using an ultrasonicprobe. To this reconstituted lipid, 6 ml of perfluorooctyl bromide(PFOB, Exfluor Research Corp.) was added and a coarse emulsion wasformed using the ultrasonic probe. This coarse emulsion was transferredto a microfluidizer (M-110S, Microfluidics Corp.) and processed for 4minutes at a pressure of approximately 17,000 PSI. The resultingemulsion was transferred to a 30 ml serum vial under argon and stored at4° C.

Animal Studies

Male mdx mice (strain C57BL/10ScSn-Dmdmdx/J) and age-matched controls(strain C57BL/10SnJ) were purchased from The Jackson Laboratory (BarHarbor, Me.). Starting at age 14 weeks, the mice were injected twiceweekly for four weeks with either plain nanoparticles (no drug, n=18 formdx, n=4 for control) or nanoparticles loaded with 0.275% rapamycin(n=16 for mdx, n=5 for wild-type). Dosage was 1 mL emulsion per kg bodyweight, delivered through the tail vein. The same treatment regimen wasrepeated on a subset of each group of mice at age 34 weeks in order toassess age-related changes in strength and treatment effectiveness.Cohort size for each age group was n=7 for mdx/no drug, n=8 formdx/rapamycin, n=4 for control/no drug, and n=5 for control/rapamycin.No animals in any group demonstrated any apparent adverse effects fromthe treatment at either 14-18 week (“young”) or 34-38 week (“aged”) timepoints.

Treatment effectiveness was determined by measuring forelimb gripstrength within one week before beginning each treatment regimen, andsubsequently within one week after treatment completion. Strengthtesting was performed in blinded fashion by an experienced technicianusing a grip meter attached to a force transducer (E-DF 002 DigitalForce Gauge, Chatillon Force Measurement Systems, Largo, Fla.). Thetests relied on the animal's instinct to grab hold as it was pulledbackward. Each mouse was grasped by the tail and encouraged to grab atrapeze bar attached to the force transducer using its forelimbs. Themouse was then pulled away and the peak force was recorded on a digitaldisplay. This procedure was repeated five times sequentially for eachanimal. The three highest readings were averaged and normalized by theanimal's weight to give the strength score.

A separate study was conducted in which rapamycin was administered tomdx and wild-type mice orally. Mice aged 14 weeks were given oral dosesof a rapamycin solution (0.067 mg rapamycin/kg body weight) twice perweek for a four-week period, mimicking the previous nanoparticle IVinjection protocol. The dose volume was set at this level in order toyield an equivalent full body dose to the animals in the nanoparticleinjection studies, assuming oral bioavailability to be approximately10%. Rapamycin powder was solubilized in 190-proof ethanol at 1 mg/mL.This mixture was then diluted 50% in a 1:1 mixture of dextrose andwater. A placebo was also formulated that omitted the rapamycin. Thetreatment solution was administered with a micropipette, typically 40-50μL per mouse. Forelimb grip strength was measured before and after thefull treatment regimen. There were three treatment groups: mdx micegiven rapamycin (n=6); control mice given rapamycin (n=6); and mdx micegiven placebo (n=6).

Tissue Homogenization

Muscle tissue were extracted from the mdx mice and homogenized in 0.5 mLof RIPA buffer with 1 mM PMSF, Complete Protease Inhibitor Cocktail(Roche, Indianapolis, Ind.), and Phosphatase Inhibitor Cocktail (Roche)using a glass grinding tube. The tissue homogenates were centrifuged at10,000×g for 10 min at 4° C. and the supernatant was stored at −80° C.

Western Blot Analysis

Proteins in tissue homogenates were resolved on a NuPAGE Novex 4-12%Bis-Tris Gel (Invitrogen NP0336BOX, Carlsbad, Calif.) and transferred to0.2 μM nitrocellulose membranes (Invitrogen LC2000). Membranes wereblocked in 5.0% milk in TBS (G Biosciences R029, St. Louis, Mo.) with0.05% Tween-20 and incubated with the following primary antibodies:rabbit anti-pS6 (1:1000, Cell Signaling Technology 4857, Boston, Mass.),rabbit anti-S6 (1:1000, Cell Signaling Technology 2217), rabbitanti-LC3B (1:2000, Sigma, St. Louis, Mo.), rabbit anti-Beclin1 (1:1000,Cell Signaling Technology), goat anti-actin (Santa Cruz Biotech).Corresponding secondary antibodies were used at 1:5000. Protein bandswere visualized using either ECL Western Blotting Substrate (Pierce32106, Rockford, Ill.) or Super Signal West Femto Maximum SensitivitySubstrate (Pierce 34095, Rockford, Ill.). Western blot image was used tocalculate relative protein expression using densitometry with the opensource image analyais package ImageJ (W. S. Rasband, NIH, Bethesda, Md.,http://imagej.nih.gov/ij, 1997-2011). Values were normalized to proteinbands on ponceau stained membranes (muscle lysates) or actin (celllysates) and reported as fold change compared to the control,non-treated sample.

Cell Culture

C2C12 cells were obtained from ATCC (Manassas, Va.) and maintained inDMEM supplemented with fetal bovine serum in a 37° C. incubator with 5%CO₂. Cells were differentiated by culturing in DMEM+2% horse serumfor >4 days. Prior to differentiation, cells were visually checked forconfluency. For autophagy flux assays, cells were treated with variedconcentrations of nanoparticles, nanoparticles loaded with rapamycin,and equivalent doses of rapamycin dissolved in DMSO. To block flux,bafilomycinA dissolved in DMSO was added to cell culture media. Cellswere harvested in RIPA buffer (10 mM Tris-HCL (pH 7.5), 150 mM NaCl,1.0% IgepalCA-630, 0.5% sodium deoxycholate, 0.1% sodium dodecylsulfate, 1 mM EDTA, 5% glycerol) with 1 mM PMSF, Complete ProteaseInhibitor Cocktail (Roche, Indianapolis, Ind.), and PhosphataseInhibitor Cocktail (Roche). Cell lysates were collected by saving thesupernatant after centrifuging the sample at 10,000×g for 10 min at 4°C. Western blotting was done for LC3 as described above.

Statistics

Statistics were done in collaboration with Dr. William Shannon andcolleagues in the Department of Medicine Biostatistics Core using SASsoftware (SAS Institute, Cary, N.C.).

Example 1 Rapamycin-Loaded Nanoparticles Improve Strength in Mdx Animals

An oral and a nanoparticle-based formulation of rapamycin were comparedfor ability to improve a clinically significant performance factor,muscle grip strength. 14-week old mdx and wild-type mice were treatedwith eight doses of intravenous nanoparticles over four weeks andstandardized grip strength measurements were obtained on each animalbefore and after therapy. FIG. 1 shows that grip strength increasedsignificantly when rapamycin-loaded nanoparticles (RNP) were employed astherapy (30% increase in strength). Unexpectedly, when NP alone wereemployed as therapy, grip strength also increased modestly (FIG. 1A) by8%. When compared to published data collected in the same way used here,this is a remarkable increase in strength as untreated mdx animalstypically show a 14.6%+/−5.1% decrease in strength [13]. To determinewhether the increase in strength achieved with rapamycin-loadednanoparticles was due to the drug alone, animals were treated with oralrapamycin administered at 10× the dose provided in the intravenousnanoparticle formulation to account for an expected 10% oral absorptionrate [24-27]. Age-matched wild-type mice exhibited no significantincrease in strength when treated with rapamycin-loaded nanoparticles ororal rapamycin (FIG. 1B). However, during this age range, wild-typeanimals typically demonstrate a decrease in strength per weight(−6.6%+/−6.4%), so the increase seen in wild-type animals treated withnanoparticles is interesting.

The cumulative dose of rapamycin given to the animals in therapamycin-loaded nanoparticle treatment group was within the limits ofrecommended oral individual dose for patients receivingimmunosuppressive therapy when accounting for 18% oral absorption inhumans. Further, the intravenous dose used here was approximately 7-foldless than the calculated absorbed oral dose administered to mdx mice byEghtesad and colleagues to improve muscle pathology [14]. These dataindicate that at clinically relevant dose of oral rapamycin for mdxanimals, and one that scales up to 4-fold greater than the recommendedoral dose for patients, no improvement in strength was obtained. Insharp contrast, the standard dose of rapamycin administered in NPformulations provided marked improvement in grip strength after only 8i.v. doses. Thus, oral dosing of rapamycin will not affect strength inthis model, whereas nanoparticle dosing delivering conventional drugdoses appears effective.

To determine whether the increase in strength was both repeatable andindependent of the age at which the animals were treated, a subset oftreated young animals were given a drug holiday from weeks 18-34, thenthe nanoparticle dosing was repeated. FIG. 1C shows that over this drugholiday interval, strength declined as anticipated; but that after therepeat dosing of i.v. RNP, strength recovered in the older mdx animals(p=0.008, linear contrast model). The drug holiday data indicatestrength declines when off of the drug but that the treatment isreproducible when re-administered and effective over a diverse timeinterval even late in the disease time course. The observation ofstrength increase was therefore independent of age, confirming theefficacy of RNP in both younger and older subjects. No significant trendwas observed in wild-type mice (FIG. 1D).

Example 2 Systemically Delivered Nanoparticles are Delivered to MdxMuscles

To prove that the nanoparticles themselves are delivered to muscletissue, transmission electron microscopy (TEM) and fluorine spectroscopywere performed on excised mouse muscles. Fourteen week-old mdx mice andage-matched wild-type mice were treated by lateral tail vein injectionfor four consecutive days with 1 ml/kg RNP, NP, or saline. Muscles frommdx animals exhibited nanoparticles entrained in and around the musclecells (FIG. 2A). The particles are distinguishable from disease-inducedlipid droplet accumulation by the presence of a dark halo around thenanoparticles. Fluorine spectroscopy to register the ¹⁹F PFOB core ofthe NP was performed to quantify the concentration of NP in muscletissue (FIG. 2B). Concentrations of nanoparticles in muscle tissues werecalculated by using a standard curve for ¹⁹F spectroscopy. Becausebaseline levels of ¹⁹F in tissues are negligible, it can be concludedthat the spectroscopy signal is solely due to the presence of particlesin the muscle. Two-tailed t-tests showed no difference between particleuptake when rapamycin was incorporated into the particles for allmuscles tested.

Example 3 Rapamycin Nanoparticles Decrease pS6 Levels

To demonstrate that the drug is acting on the appropriate target once itreaches the muscle, lysates from the muscle were probed from the shorttime course experiment above for phosphorylated S6. S6 is downstream ofmTORC1, so that blocking mTORC1 with rapamycin should cause a decreasein pS6 levels. Indeed, in diaphragm, triceps, biceps, and gluteus, S6levels were decreased in the mdx animal treated with rapamycin-loadednanoparticles when compared to mice treated with nanoparticles alone(FIG. 2C). Interestingly, the nanoparticles cause an increase in pS6levels when compared to saline treated animals. Therefore, the particleis inducing signaling through mTORC1. Adding rapamycin to the particledecreases the amount of signaling, but does not cause it to return tobaseline levels. In addition to decreasing the levels of phosphorylationof S6, RNP treatment results in attenuated and more diffuse staining inthe mouse diaphragm when compared to the strong, tight staining seen inanimals treated with nanoparticles alone (FIG. 2D).

Example 4 Nanoparticle Treatment Restores Autophagy

To examine a potential mechanism by which rapamycin-nanoparticles areimproving strength in mdx animals, another cohort of the short termtreated animals received i.p. injections of colchicine to enablemeasurement of autophagic flux as previously reported [28]. In thediaphragm, autophagy levels were restored to normal with bothnanoparticle and rapamycin-loaded nanoparticle treatment as measured byLC3B-II accumulation even when blocked with colchicine, indicative of apreviously unreported defect in autophagy in the mdx mouse (FIG. 3A-D).The apparent defect in autophagy in mdx mice is also demonstrated by areduction in Beclin-1 and BNIP3 expression in the diaphragm whencompared to an age-matched control animal (FIG. 3E).

To validate the induction of autophagy in muscle cells by nanoparticles,C2C12 cells were allowed to grow to confluence and then differentiatedinto myotubes. These myotubes were subjected to treatment withnanoparticles. To assess autophagy flux, additional samples were treatedwith bafilomycin to block autophagy progression. LC3B levels were higherin cells treated with nanoparticles of rapamycin-loaded nanoparticles,thereby suggesting an induction of autophagy, and indicating thatbasally suppressed autophagy can be rescued by this therapeutic strategy(FIG. 3F).

Discussion for Examples 1-4

It has been shown for the first time that rapamycin-loaded nanoparticlesimprove strength in a mouse model of Duchenne muscular dystrophy andthat the observed improvement may be due to restoring a disease-relateddefect in autophagy. Previous work has demonstrated improvement inmuscle pathology when mdx animals were treated with oral rapamycin or amicroparticle intramuscular (i.m.) depot injection of rapamycin [14]. Inthat study, immune infiltration was decreased and muscles were healthieras judged by increased proliferative capacity and decreased necrosis.However, no physiological metrics were presented to conclude that thisapproach would be efficacious as a clinical strategy. Here, an increasein strength was demonstrated after systemic treatment withrapamycin-loaded nanoparticles that is both repeatable and capable ofenhancing performance in both younger and older subjects. Interestingly,this approach achieves the strength increase with systemic rapamycindosing at a quarter of the initial rapamycin depot injection reported byEghtesad et al. [14].

It has also been demonstrated that the nanoparticle formulation ofrapamycin is key to achieving this strength increase, as rapamycin givenorally at pharmacological doses to compensate for decreased oralbioavailability does not improve strength in mdx animals. The potentialclinical utility for nanoparticle-based drug delivery derives from theconcept of decreasing systemic dosing while increasing local delivery bymolecular targeting of the particles to specific cell types [29, 30].Additionally, the incorporation of traditional chemotherapeutics intonano- and microcarriers has increased their circulation time andtherefore increased therapeutic effect simply by having the drug clearedmore slowly while being retained in particle that theoretically exertsless effect on normal than on pathological tissues [31].

Interestingly, it could be that the nanoparticle carrier itself may havesome strength promoting capacity. Whether this is due to the addition oflipids to the cell thereby stabilizing the dysfunctional muscle cellmembrane, the initiation of undescribed cell signaling events, or otherfactors is unclear. Regardless, the strong enhancement of S6phosphorylation seen in the mdx animals after nanoparticle treatmentsuggests that the particles do drive the mTORC1 cell signaling pathway.Previously it has been shown that protein synthesis is shut off in thehigh intracellular calcium environment found in muscles of musculardystrophy patients and mouse models [32, 33]. Possibly some of thebenefit of the nanoparticle drug delivery is due to reinstatement ofprotein synthesis via promotion of mTORC1 signaling.

The enhancement of S6 phosphorylation is particularly interesting giventhat the diaphragm of mdx mice is reported to be unable to increase mTORactivity with age [34]. Considering that respiratory and cardiac failureare the major causes of death in patients with DMD, the underlyingmolecular cause of this failure may be due to a lack of capacity toregenerate muscle fibers, especially in cardiac and diaphragm musclecells as these are in constant use throughout life and therefore mostlikely to exhaust regenerative capacity sooner than other muscles. Theaddition of rapamycin to the particle decreased the level of pS6, butdid not reduce it to baseline, suggesting that some signal promotion wasstill occurring in these cells, which may be one factor contributing toan increase in strength.

Skeletal muscle, including the diaphragm, comprises different fibertypes, each of which prefer different methods of energy derivation.Fibers that utilize oxidative phosphorylation are thought to betterresist fatigue as compared to the fast twitch fibers that use glycolysis[35]. Interestingly, mTOR also plays a role in metabolism as it has beenshown to transcriptionally activate mitochondrial genes related tooxidative phosphorylation [36]. Further, completely blocking mTORC1 inthe muscle via knocking out raptor [37] or knocking out mTOR [38] causesa decrease in oxidative capacity and increase in glucose and glycogenuptake, respectively. Therefore, it may be the case that the mTORC1activation observed by an increase in S6 phosphorylation in animalstreated with nanoparticles may be promoting oxidative phosphorylation inthese muscles and thereby enhancing the capacity of fatigue-resistantmuscle fibers. Unlike the studies using genetic manipulation, our use ofrapamycin did not completely block the mTORC1 signal and may thereforebe permissive of this phenomenon.

Rapamycin also exhibits mTORC1 independent effects when it binds toFKBP12 on the ryanodine receptor. Previous studies suggest that bindingof rapamycin disrupts the ryanodine receptor's functions and thereforewould be expected to elicit dysfunctional calcium handling [39, 40].However, in mdx animals, the ryanodine receptor itself appears to bedysfunctional [41]. Perhaps it is the case that the addition ofrapamycin acts to block some of these receptors and help modulate a morenormal calcium handling or acts to decrease the expression of thereceptors as has been previously reported [42].

The work presented here demonstrates restoration of autophagy in themuscles of mdx animals when they are treated with rapamycin-loadednanoparticles and in C2C12 myotubes in culture. Autophagy is a bulkdegradation pathway that is used to recycle amino acids and othercellular building blocks. Originally demonstrated to be a normalresponse to nutrient stress, dysfunctional autophagy is now understoodto play a role in a broad range of diseases including various cancers,diabetes, heart disease, and neurodegenerative disorders [43, 44]. Inthe field of neuromuscular disorders, inclusion-body myopathy has beenshown to be caused by mutations in a protein necessary for properautophagy [45]. Defects in autophagy also play a role in Pompedisease[46].

More recently, defects in autophagy has been reported in collagen-6knock-out mice, a mouse model of Bethlem myopathy and Ullrich congentialmuscular dystrophy [15]. Genetic, dietary, and pharmaceuticalapproaches, including rapamycin, for inducing autophagy in the Col6a−/−mice all resulted in improvement in the dystrophic phenotype. Here, weillustrate increased autophagy in mdx mouse muscles afterrapamycin-nanoparticle treatment. While it has been proposed thatinduction of autophagy by rapamycin is cell-type specific with musclecells being insensitive to rapamycin [47, 48], in sharp contrast we findthat when administered on a nanoparticle, rapamycin is capable ofinducing autophagy in the muscles of mdx animals. The ability to repeatthis observation after a drug holiday in aging subjects is conclusivefor the effect.

This latter effect is most exciting and clinically relevant, as theincrease in strength after treatment is not restricted to the early tomid stage of the disease in the mouse model, but can also improvestrength much later in the course of the disease. This observation ishopeful as previous studies have demonstrated improvement in strength inthe mdx animal very early in the disease course, but have not provenbeneficial as the disease progresses [13]. Further to clinicaltranslation, it was demonstrated the efficacy of rapamycin-loadednanoparticles at drug doses lower than would be administered orally topatients. Unfortunately, there is no apparent benefit to strength whenthe plain drug is given orally, even at pharmacological doses.Additionally, it would be expected that patients might prefer i.vinjections rather than multi-site microparticle intramuscular depotinjections as previously reported to improve muscle pathology [14].Because rapamycin is an approved agent for other diseases, and becausethese perfluorocarbon nanoparticles have demonstrated an excellentsafety record in clinical trials as a blood substitute at far greaterdoses than used in this study [49-51], or in other experimental studieswhen used for targeted molecular imaging and therapeutics [52-55], therapamycin nanoparticle construct could represent a promising candidatefor trials in muscular dystrophy.

References for Examples 1-4

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Example 5 Rapamycin-Loaded Nanoparticles Improve Ejection FractionStrength in Older Mdx Animals

The effect of rapamycin-loaded nanoparticles on cardiac muscle strengthin mdx and wild type animals was measured. Seven 17 month old mdx mice,and nine 17 month old wild type (WT) mice were separated into rapamycintreated groups (rapamycin-treated mdx mice N=3; rapamycin-treated WTmice N=5) and untreated groups (untreated mdx mice N=4; untreated WTmice N=4). The rapamycin treated groups received eight evenly separatedIV injections of rapamycin-loaded nanoparticles in four weeks (0.275 mol% rapamycin in perfluoro-octyl bromide nanoparticle, 1.5 mL/g bodyweight). All mice were lightly anesthetized with isoflurane for imagingat the age of 18 month. The body temperature was maintained with aheating pad and thermistor-controlled heating lamp. Heated ultrasoundcoupling gel was applied to the shaved chest area. Parasternalshort-axis (SAX) and parasternal long-axis (LAX) views of the leftventricle were acquired using a commercially available ultrasoundscanning system (Spark, Ardent Sound, Inc., Mesa, Ariz.) with ahigh-frequency linear array (16 MHz, 128-element). Waveforms weresampled at 66.67 MHz. Two hundred frames of cardiac data were acquiredfor each view at a frame rate of 152 Hz, with each frame consisting of128 A-lines. Each loop thus consisted of between 8 and 12 heart cycles.RF data was analyzed in custom plugins written for ImageJ (Rasband, W.S., ImageJ, U.S. National Institutes of Health, Bethesda, Md.). Theresulting image loops were scaled to a resolution of 0.05 mm/pixel.Ejection fraction was computed using ImageJ by manually tracing theventricular endocardium border at systole and diastole in the SAX viewfor each beat and recording the area region of interest (ROI). Leftventricular volume at systole (or diastole) was estimated by computingthe volume of an ellipsoid having a circular cross-section equal to themean systolic (or diastolic) ROI area and length equal to the meansystolic (or diastolic) measured ventricular length in LAX. Ejectionfraction (EF) was then computed as the ratio of the difference in volumeof this ellipsoid between diastole and systole.

EF was improved in the treated mdx mice (67±4.3%), compared to theuntreated mdx mice (54±4.7%) (FIG. 4A). EF in the treated WT mice wasnot improved (FIG. 4B), consistent with the discovered function ofrapamycin-loaded nanoparticles in improving muscle strength ofdeteriorating muscle tissue, but not muscle strength of normal muscletissue.

Example 6 Rapamycin-Loaded Nanoparticles Improve Pull Strength in OlderWild Type Animals

Five 17 month old wildtype mice (BL/10, Jackson Laboratories, BarHarbor, Me.), and four 17 month old mdx mice were weighted and examinedfor forelimb strength before (FIG. 5A) and after rapamycin nanoparticletreatment (FIG. 5B). The rapamycin treatment consisted of 0.275 mol %rapamycin in perfluoro-octyl bromide nanoparticle administered at 1.5mL/g body weight, twice per week, for four weeks. Strength testingconsisted of five separate measurements using a trapeze bar attached toa force transducer that recorded peak generated force (Stoelting,Wood-Dale, Ill.). Mice instinctively grab the bar with their forepawsand continue to hold while being pulled backwards by the tail, releasingonly when unable to maintain grip. The resulting measurement wasrecorded and the three highest measurements were averaged to give thestrength score.

After treatment, strength(g) per body weight(g) in WT mice was improvedby 27% from 2.33±0.06 to 2.95±0.13 (FIG. 5C). Strength in the treatedmdx mice was not improved (FIG. 5D), consistent with the anticipatedlack of efficacy toward skeletal muscle strength in the end stages ofthe disease process. Also, as the heart disease in mdx mice and DMDpatients is known to develop later in the disease process than does theskeletal myopathy, it is not surprising that efficacy is observedregarding improved heart function in the later stages of the disease.

Example 7 Fluorescence Staining of Nanoparticle and Rapamycin Depositionin the Diaphragm of Mdx Mice

A mouse diaphragm muscle was excised from an mdx mouse treated withrapamycin-loaded nanoparticles (FIG. 6A). The nanoparticles wererhodamine-labeled, and the rapamycin was labeled with Cy-7. Thediaphragm muscle exhibited deposited nanoparticles entrained in andaround the muscle cells (FIG. 6B). Rapamycin showed both punctate anddiffuse staining, indicative of diffusion of rapamycin into distantmuscle tissues (FIG. 6C).

1. A method for increasing muscle strength in a subject, the methodcomprising administering rapamycin-loaded nanoparticles to a subject inneed of increased muscle strength.
 2. The method of claim 1, wherein thesubject has muscular dystrophy.
 3. The method of claim 1, wherein thesubject is suffering from muscle weakness resulting from aging.
 4. Themethod of claim 1, wherein the subject is suffering from muscle weaknessresulting from a traumatic injury or surgery.
 5. The method for claim 1,wherein the administration of rapamycin-loaded nanoparticles inducesautophagy of muscle cells.
 6. The method for claim 1, wherein theadministration of rapamycin-loaded nanoparticles attenuates muscledestruction.
 7. The method for claim 1, wherein the rapamycin-loadednanoparticles are administered intravenously.
 8. The method for claim 1,wherein the rapamycin-loaded nanoparticles comprise between about 0.1and 0.5% rapamycin.
 9. The method for claim 1, wherein therapamycin-loaded nanoparticles are administered at least once a week.10. The method for claim 1, wherein 1 mL/kg of the rapamycin-loadednanoparticles are administered at least once a week. 11.-17. (canceled)18. A method for attenuating muscle destruction in a subject, the methodcomprising administering rapamycin-loaded nanoparticles to a subjectexperiencing muscle destruction.
 19. The method for claim 18, whereinthe administration of rapamycin-loaded nanoparticles induces autophagy.20. The method for claim 18, wherein the rapamycin-loaded nanoparticlesare administered intravenously.
 21. The method for claim 18, wherein therapamycin-loaded nanoparticles comprise between about 0.1 and 0.5%rapamycin.
 22. The method for claim 18, wherein the rapamycin-loadednanoparticles are administered at least once a week.
 23. (canceled) 24.A method for inducing autophagy in the muscle cells of a subject, themethod comprising administering rapamycin-loaded nanoparticles so thatautophagy is increased in the muscle cells of the subject.
 25. Themethod for claim 24, wherein the administration of rapamycin-loadednanoparticles attenuates muscle destruction.
 26. The method for claim24, wherein the rapamycin-loaded nanoparticles are administeredintravenously.
 27. The method for claim 24, wherein the rapamycin-loadednanoparticles comprise between about 0.1 and 0.5% rapamycin.
 28. Themethod for claim 24, wherein the rapamycin-loaded nanoparticles areadministered at least once a week.
 29. (canceled)